Ionizable gas display device with segmented electrode pattern



June 20, 16? R BOvVERMAN 3,327,154

TPOIJE PATTERN IONIZABLE GAS DISPLAY DEVICE WITH SEGMENTED ELEC FiledMarch 24, 1965 o I 2 3 4 5 s 7 a 9 DECODING MATRIX INVENTOR. EDWIN R.BOWERMAN TORNE Y.

United States Patent corporation of Delaware Filed Mar. 24, 1965, Ser.No. 442,377 5 Ciaims. (Cl. 313-1095) This invention relates to displaydevices and more particularly to a glow discharge display device.

A glow discharge display device is generally comprised of a transparentenvelope which contains an anode electrode, a number of cathodeelectrodes, and an ionizable gas capable of supporting a glow discharge.The application of a suitable D.C. voltage between the anode electrodeand a selected cathode electrode results in the breakdown of the gas andcurrent fiow through the gas from the cathode to the anode. Thisbreakdown of the gas is characterized by a glow at the surface of theselected cathode.

The shape of the cathode elements determines the pattern of the glowdischarge of the gas and many difierent alpha-numeric cathodeconfigurations have been employed. One particularly useful configurationis a segmented cathode having a figure-eight shape and comprising sevensubstantially equal segments. The anode electrode may be formed in thetwo central portions of the figure-eight or a wire mesh screen may bespaced from the entire pattern. By applying the DC. voltage between theanode and selected cathode segments, the glow discharge depicts anynumeral from 1 to 0. In addition, other configurations have beenemployed to permit the representation of any desired letter and/ ornumeral.

In the construction of display devices of this type the segments of thecathode electrode are generally formed by engraving or other graphicarts techniques and are mounted on a mica insulator. The cathodesegments are provided with lugs which extend through the insulator andserve to position and lock the segments in place.

A common anode may be provided by a wire mesh screen which is assembledover the cathode segments and is locked in place to the mica insulator.The assembly is then provided with a supporting base and gas-containingenvelope. The electrical connections within the display device areprovided by wiring each cathode electrode segment to an external pinconnector. The wire used must be insulated to prevent any glow dischargefrom occurring thereat.

The display device construction is found to have certain disadvantages.These disadvantagesarise from the fact that each cathode segment must besupported on the insulator by mounting lugs and then individually wiredto an external pin connector on the envelope base. Since the number ofcathode segments may be thirteen or greater for alpha-numeric cathodeelectrodes, the mounting and wiring steps performed during assembly haveresulted in an increase in cost, complexity and size of the manufactureddisplay device.

Accordingly, an object of the present invention is the provision of aglow discharge display device wherein the segmented cathode electrodeand the electrical connections thereto are formed on One side of asuitable substrate.

Another object is to provide a glow discharge display device wherein thecathode electrode and the electrical connections to the segments thereofmay be formed by graphic arts techniques on a glass substrate.

A further object is to provide a glow discharge display device in whicha cathode pattern and corresponding glow discharge may be formed on morethan one surface of the substrate. I

In accordance with the present invention, a display device of the glowdischarge type is provided in which a plurality of conducting paths areformed on one surface of a substrate. Over-lying a portion of theconducting paths is an insulating layer, which may be a glass fritsuitably glazed. The insulating layer is provided with a plurality ofapertures extending therethrough. Each of the apertures in theinsulating layer is positioned to register with one of the conductingpaths formed on the glass substrate.

A segmented electrode pattern is then formed on the insulating layerwith each segment being formed about at least one of the apertures inthe insulating layer. Each segment is electrically connected through anaperture to a conducting path. The connections may be readily attainedthrough the use of evaporation or metal spray techniques in forming theelectrode pattern.

The electrode pattern is then covered by an envelope containing anionizable gas having a pressure capable of sustaining a glow discharge.The envelope is hermetically bonded to the insulating layer. By applyinga suitable DC. voltage between conducting paths connected to selectedsegments in the electrode pattern and at least one conducting pathcoupled to an unselected segment of said electrode pattern which rendersthe selected segments cathodic, a glow discharge is provided along thesurface of the selected cathode segments.

The display device is formed entirely on one side of the substrate sothat no connecting holes need be formed in the substrate. As a result,inexpensive substrate materials, such as sheet glass, wherein it isgenerally difiicult to form holes, may be readily employed.

A further advantage is realized in the afore-discussed construction inthat restricting the graphic arts techniques to one surface of thesubstrate permits similar operations to be concurrently performed onmore than one surface of the substrate. Thus, a display device may beformed on each of the opposing broad-area surfaces of a relatively thinsubstrate. In addition, a plurality of display devices may be formed oneach surface of a large-area substrate with a single gas-filled envelopeprovided on each surface.

Further features and advantages of the invention will become morereadily apparent from the following description of specific embodimentswhen viewed in conjunction with the accompany drawings, in which FIG. 1is an exploded view of one embodiment of the invention;

FIG. 2 is a side view in section of the embodiment of. FIG. 1 takenalong lines 2-2; and

FIG. 3 is a perspective view of a second embodiment.

Referring to the display device of FIGS. 1 and 2, substrate 10 is shownhaving a network comprising a pluralityof conducting paths 11 formed onone surface thereof. The substrate 10 may be of glass or other suitablevacuum tight ceramic.

The conducting paths 11 may be formed on the substrate by conventionalgraphic arts techniques. One suitable technique is to silk screen ametallic gold luster on to the substrate and then heat the substrate tobond the gold thereto. Also, transparent conducting paths may be formedby spraying a stannic chloride solution onto a hot glass substrate. Theexcess conductor is then removed by protecting the conducting paths witha stencil while sandblasting the exposed surface.

Apertured insulating layer 12 is formed on the substrate overlying theinner portion of the conducting paths. This layer may advantageously beapplied by spraying a layer of glass frit on the substrate, removing thefrit at selected locations to form apertures 13 and heating .theassembly to glaze the frit. The apertures 13 are located in registrationwith a corresponding conducting path. The insulating layer may be eitheropaque or transparent and in practice, the use of a black glass frit hasbeen found to provide increased contrast between the glow discharge andthe background. In addition, the insulating layer need not be uniform inthickness so that increasing the thickness of the central portion of thelayer can be used to increase the angle at which the display device canbe viewed.

The final segmented electrode pattern comprising segments 14 and 15,herein termed the cathode and anode segments respectively, is thenapplied over the insulating layer 12. The particular electrode patternshown is a figure-eight containing segments 14 with segments 15centrally located therein. One method of applying the electrode patternis to first mask the surface and then deposit evaporated aluminumthereon. It will be noted that many other methods, such as metal sprayor electroless plating, may be employed. The particular pattern applieddepends on the application mask.

Each segment of the electrode pattern includes at least one aperture.During the application of these segments to the insulating layer, aportion of the metal deposited enters the apertures to provide theelectrical connection between a segment and a corresponding conductingpath. This is shown in FIG. 2 wherein the apertures 13 are filled withthe metal deposited to form the electrode pattern.

An envelope 16 is hermetically mountedon insulating layer 12. Theenvelope may be formed of glass and sealed to the layer, 12 by a glasssolder. The envelope is evacuated of air and filled with an ionizablegas suitable for supporting a glow discharge, for example, argon or neonat a pressure of about 30 mm. of Hg at room temperatures.

The conducting paths 11 are carried to the edge of substrate and may beplugged into printed circuit board connector 17 having a number ofspring clips 18 thereon. As shown in FIG. 1, anode segments are coupledthrough their corresponding apertures to a common conducting path 11 andto spring clip 18' while each cathode segment 14 is coupled to anindividual conducting path and spring clip. The application of a voltageof the order of 150 volts D.C. between conducting paths connected toselected cathode segments and conducting path 11, having a polarity suchthat the selectedsegments are cathodic with respect to the ionizablegas, results in a glow discharge of the gas. This glow discharge occurson the surface of the selected cathode segments so that selectingdifferent segments permits different characters to be displayed. To thisend, anode segments 15 are connected. to ground at spring clip 18' whilethe cathode segments are connected to one end of decoding matrix 30. Theother end of matrix 30 is connected through selector switch 31 tonegative DC. voltage source 32. The decoding matrix is of conventionaldesign with the position of the selector switch determining which of theoutputs and the corresponding conducting paths are energized. Since thevoltage required to sustain a glow discharge is less than the voltagerequired to' initiate it, the decoding matrix should provide equalcurrent limit ing resistances for each output. Alternatively, a separatecurrent limiting resistor may be connected in series with each springclip 18.

While the above description refers to an embodiment which displays onecharacter, the present invention may be constructed so as to displayseveral characters on each surface of the substrate. This is shown inthe embodiment of FIG. 3 wherein a single substrate is utilized to forma display device for displaying two characters on each broad areasurface of the substrate.

Conducting paths 21 are formed on each side of substrate 20 and comprisefour networks of the conducting paths 11 shown in FIG. 1. The conductingpaths 21 are covered by a pair of insulating layers 22 having apertures23 therein. The apertures register with a corresponding conducting path.

A pair of segmented electrode patterns comprising cathode segments 24and anode segments 25 is formed on each of the insulating layers 22.Each segment is coupled to a conducting path through a correspondingaperture.

An envelope 26 is hermetically mounted on each insulating layer 22 andis filled with an ionizable gas having a pressure capable of sustaininga glow discharge therein. The application of a voltage between selectedcathode segments of each pattern and their respective anode seg-, mentsprovides a display of two characters on each side of the substrate.

' Although the substrate is shown relatively thin, other substrategeometries may be employed with different electrode patterns beingformed on one or a plurality of the surfaces thereof. While the abovedescription refers to specific embodiments, it is understood that manymodifications and variations may be made therein without departing fromthe spirit and scope of the invention.

What isclaimed is:

1. A display device of the type wherein a glow discharge of a confinedionizable gas is used to display information which comprises (a) asubstrate,

(b) a plurality of conducting paths formed on at least one surface ofsaid substrate,

(c) an insulating layer formed on said surface of the substrate andoverlying a portion of said conducting paths, said insulating layerhaving a number of apertures therein in registration with saidconducting i paths, at least one aperture being in registration witheach of said conducting paths,

((1) a segmented electrode pattern formed on said insulating layer andextending through said apertures to said conducting paths, and

(e) an envelope mounted on said insulating layer for containing saidionizable gas, the application of a voltage between conducting pathsconnected to selected segments and at least one conducting pathconnected to an unselected segment of said electrode pattern resultingin a glow discharge along the surface of the selected segments.

2. A display device of the type wherein a glow discharge of a confinedionizable gas is used to display information which comprises (a) asubstrate,

(b) a plurality of conducting path networks formed on at least onesurface of said substrate,

(c) an insulating layer formed on said surface of the substrate andoverlying a portion of said conducting paths, said insulating layerhaving a number of apertures therein in registration with saidconducting 1 paths, at least one aperture being in registration witheach of said conducting paths,

((1) a plurality of segmented electrode patterns formed on saidinsulating layer and extending through said apertures to said conductingpaths, and

(e) an envelope mounted on said insulating layer for containing saidionizable gas, the application of a voltage between conducting pathsconnected to selected segments and at least one conducting pathconnected to an unselected segment of said elect-rode patterns resultingin a glow discharge along the surface of the selected segments.

3. A display device of the type wherein a glow discharge of a confinedionizable gas is used to display in-.

formation which comprises (a) a substrate, (b) a plurality of conductingpath networks formed on the surfaces of said substrate, (c) aninsulating layer formed on said substrate and overlying a portion ofsaid conducting paths, said insulating layer having a number ofapertures therein in registration with said conducting paths, at leastone aperture being in registration with each of said conducting paths,

(d) a plurality of segmented electrode patterns formed on saidinsulating layer and extending through said apertures to said conductingpaths, and

(e) envelope means mounted on said insulating layer for containing saidionizable gas, the application of a voltage between conducting pathsconnected to selected segments and at least one conducting pathconnected to an unselected segment of said electrode patterns resultingin a glow discharge along the surface of the selected segments.

4. A display device of the type wherein a glow discharge of a confinedionizable gas is used to display information which comprises (a) asubstrate,

(b) a plurality of conducting paths formed on said substrate,

(c) an insulating layer formed on said substrate and overlying a portionof said conducting paths, said insulating layer having a number ofapertures therein in registration with said conducting paths, at leastone aperture being in registration with each of said conducting paths,

(d) a segmented cathode electrode pattern formed on said insulatinglayer and extending through said apertures to said conducting paths,

(e) anode electrode means formed on said insulating layer and extendingthrough at least one aperture to said conducting paths, and

(f) an envelope mounted on said insulating layer for containing saidionizable gas, the application of a voltage between conducting pathsconnected to selected segments and at least one conducting pathconnected to said anode electrode means resulting in a glow dischargealong the surface of the selected segments.

6 5. A display device of the type wherein a glow discharge of a confinedionizable gas is used to display information which comprises (a) asubstrate,

(b) a plurality of conducting paths formed on said substrate,

(c) an insulating layer formed on said substrate and overlying a portionof said conducting paths, said insulating layer having a number ofapertures therein in registration with said conducting paths, at leastone aperture being in registration with each of said conducting paths,

(d) a segmented electrode pattern formed on said insulating layer andextending through said apertures to said conducting paths,

(e) an envelope mounted on said insulating layer for containing saidionizable gas,

(f) connecting means for receiving said substrate therein and contactingsaid conducting paths on said substrate, and

(g) means connected to said connecting means for applying a voltagebetween conducting paths connected to selected segments and at least oneconducting path connected to an unselected segment of said electrodepattern so that a glow discharge occurs along the surface of theselected segments.

References Cited UNITED STATES PATENTS 3,219,865 11/1965 Vodicka 3131083,231,776 1/1966 Britnell 313109.5 3,262,010 7/1966 Kazan 313109.5

JAMES W. LAWRENCE, Primary Examiner. R. JUDD, Assistant Examiner.

1. A DISPLAY DEVICE OF THE TYPE WHEREIN A GLOW DISCHARGE OF A CONFINEDIONIZABLE GAS IS USED TO DISPLAY INFORMATION WHICH COMPRISES (A) ASUBSTRATE, (B) A PLURALITY OF CONDUCTING PATHS FORMED ON AT LEAST ONESURFACE OF SAID SUBSTRATE, (C) AN INSULATING LAYER FORMED ON SAIDSURFACE OF THE SUBSTRATE AND OVERLYING A PORTION OF SAID CONDUCTINGPATHS, SAID INSULATING LAYER HAVING A NUMBER OF APERTURES THEREIN INREGISTRATION WITH SAID CONDUCTING PATHS, AT LEAST ONE APERTURE BEING INREGISTRATION WTH EACH OF SAID CONDUCTING PATHS, (D) A SEGMENTEDELECTRODE PATTERN FORMED ON SAID INSULATING LAYER AND EXTENDING THROUGHSAID APERTURES TO SAID CONDUCTING PATHS, AND (E) AN ENVELOPE MOUNTED ONSAID INSULATING LAYER FOR CONTAINING SAID INONIZABLE GAS, THEAPPLICATION OF A VOLTAGE BETWEEN CONDUCTING PATHS CONNECTED TO SELECTEDSEGMENTS AND AT LEAST ONE CONDUCTING PATH CONNECTED TO AN UNSELECTEDSEGMENT OF SAID ELECTRODE PATTERN RESULTING IN A GLOW DISCHARGE ALONGTHE SURFACE OF THE SELECTED SEGMENTS.